1. Field of the Invention
The present invention belongs to a field of electric connectors that are used to connect shielded cables having both a signal line and a ground line and enable, depending on applications, high-speed transmission of signals. The present invention relates to an electric connector having a conductive plate-shaped external conductor to which a ground terminal is grounded, and relates to an electric connector wherein the reliability of connection between a ground terminal and an external conductor is improved and its producibility is enhanced.
2. Related Art
Electric connectors for shielded cable are known, which comprise a conductive tubular external conductor, an insulating housing being contained inside the external conductor, and a signal terminal and a ground terminal both being contained inside the housing, and wherein the signal terminal is to be connected to a signal line of the shielded cable and the ground terminal is to be connected to a ground line thereof, respectively (refer to, for example, Japanese Patent unexamined publication gazette Heisei 7-94245 and Japanese Utility Model unexamined publication gazette Heisei 5-8884). In these electric connectors, connection of the ground terminal to the external conductor is effected by providing the ground terminal with an elastic piece, which can undergo elastic deformation, and making this elastic piece contact the inside of the external conductor.
In an electric connector disclosed in Japanese national publication gazette of translated version Heisei 10-500245, a signal terminal and a ground terminal are held between a housing and a cover each of which are produced by molding an insulating part on an external conductor. In this electric connector, connection of the ground terminal to the external conductor is effected by providing a groove, which is made in the housing to position the ground terminal, with an opening to expose the external conductor, and making the ground terminal contact the external conductor at the opening.
These conventional electric connectors have problems that, as the ground terminal and the external conductor are connected together by making them contact each other, if the contact between them become unstable due to some causes such as vibration, the impedance characteristics will fluctuate and prevent, for example, stable high-speed transmission of signals.
One solution to this problem may be soldering the ground terminal to the external conductor. However, it will add a soldering process and complicate the wire connection work. Moreover, as it is difficult to keep the quantity of the solder at a constant level, it will impose a new problem that the impedance characteristics will vary from product to product. This problem is also encountered when connection between a terminal and a shielded cable is made by soldering.
The electric connectors of this kind are required to be made thinner, in particular, it is desired that they are not bulky when they are used in layers.
The present invention was made in view of these points, and its objective is to provide an electric connector wherein a first insulating housing is primarily molded on a plate-shaped external conductor, a crimp-type signal terminal and a crimp-type ground terminal are engaged with the first insulating housing, and a second insulating housing is secondarily molded on them to make the ground terminal contact hard the external conductor to improve the reliability of connection between them and secure more stable impedance characteristics, and also to eliminate any soldering process to improve the producibility through reduction in work processes and equalize impedance characteristics of the products, and to realize a thinner design. Further objective of the present invention is to press the ground terminal by a core pin at the time of the secondary molding so as to effectively prevent the ground terminal from being shifted or deformed under the pressure of an insulating material being molded secondarily and the insulating material from penetrating between the ground terminal and the external conductor and causing defective connection between the ground terminal and the external conductor.
To accomplish the above-mentioned objectives, the electric connector for shielded cable according to the present invention is an electric connector, which is used for connecting a shielded cable having a signal line and a ground line. This electric connector comprises a conductive plate-shaped external conductor, an insulating first housing being primarily molded on the inside of the external conductor, a signal terminal having a contacting part at one end thereof, which contacts a counterpart terminal, and a barrel on the other end thereof, which crimps the signal line of the shielded cable, and being arranged on the inside of the first housing in one direction, a ground terminal having a contacting part at one end thereof, which contacts a counterpart terminal, and a barrel on the other end thereof, which crimps the ground line of the shielded cable, and being arranged on the inside of the first housing in the same direction as the signal terminal, a engaging mechanism for engaging the signal terminal and the ground terminal onto the first housing, and an insulating second housing being secondarily molded to sandwich the signal terminal and the ground terminal between itself and the first housing, wherein the external conductor is provided with a support protrusion, which is formed to protrude inside of the external conductor to contact the ground terminal, and the second housing is provided with a through hole, which is formed by a core pin that protrudes inward from a mold and presses the ground terminal, at a position where the second housing faces the support protrusion with the ground terminal in between.
In this electric connector for shielded cable, as the second housing is molded secondarily on the ground terminal, the ground terminal is made to contact hard the external conductor and the reliability of connection between them is improved, and in turn, more stable impedance characteristics are obtained. The signal line of the shielded cable is crimped in the barrel of the signal terminal, the ground line of the shielded cable is crimped in the barrel of the ground terminal, and the ground terminal is made to contact the support protrusion of the external conductor. As a result, there is no soldering process, and the work processes are reduced and the producibility is enhanced, and moreover, the impedance characteristics of the products are equalized. Furthermore, as the major parts are formed by overlaying the plate-shaped external conductor, the first housing, the signal terminal and the ground terminal, and the second housing, the electric connector can be made thinner.
When the second housing is molded secondarily, as the core pin presses the ground terminal against the support protrusion at the position of the through hole, the ground terminal will not be shifted or deformed under the pressure of the insulating material being secondarily molded, and the insulating material will not penetrate between the ground terminal and the support protrusion. Hence the secondary molding is effectively prevented from causing any defective connection between the ground terminal and the external conductor.
Accordingly, in the electric connector for connecting a shielded cable according to the present invention, as the second housing is molded secondarily, the ground terminal is made to contact hard the external conductor and the reliability of connection between them is improved and more stable impedance characteristics are obtained, and this allows, for example, stable high-speed transmission of signals. In this case, as the ground terminal is pressed by the core pin, the ground terminal is effectively prevented from being shifted or deformed and the insulating material is effectively prevented from penetrating between the ground terminal and the support protrusion to cause any defective connection between the ground terminal and the external conductor. Moreover, as there is no soldering process, the producibility is enhanced through reduction in the work processes and the impedance characteristics of the products are equalized. Furthermore, the electric connector can be made thinner, and this is desirable when such electric connectors are used in layers.